This invention relates generally to apparatus and methods for communicating analog communication signals, routed through a central office of a telephone system, with a plurality of remote drops in communication with the central office. The invention relates more particularly, but not by way of limitation, to apparatus for interfacing analog signals between two four-wire private lines.
With the deregulation of the telephone industry in the United States and the accompanying separation between AT&T and its regional Bell operating companies, new and different rate structures have developed based on whether a telephone circuit originates and terminates within a single local area referred to as a local access transport area (LATA), or whether the circuit crosses a LATA boundary so that the circuit is between two or more LATA's. A circuit or transmission wholly within a single LATA (an intra-LATA circuit) is within the jurisdiction of a regional, and now independent, operating company, whereas a circuit or transmission across a LATA boundary (an inter-LATA circuit) is within the jurisdiction of, and requires use of, a long-line carrier (e.g. AT&T). Under present rate structures, inter-LATA circuits are more expensive than intra-LATA circuits; therefore, it would be less expensive if when a party in one LATA has to communicate with several different locations within another LATA, the party in the first LATA could lease a single inter-LATA circuit and then establish intra-LATA circuits from that point to multiple locations in the other LATA.
The foregoing is applicable to four-wise private lines, which are dedicated communication paths through the telephone system between specific locations. To illustrate, assume that a financial record management company has a computerized financial system which updates financial records of other businesses located throughout the country (or, at least, in one or more other LATA's from where the management company is located). The financial management is implemented under control of a master computer located on the premises of the management company, which computer must communicate with computers located on the premises of the other business in the one or more other LATA's. The master computer is connected into the existing telephone system over a four-wire private line to the central office of the telephone system serving the area in which the master computer is located; this connection is through known means and establishes the master computer as what is referred to in the telephone industry as a master station demarcation point. The computers of the other businesses are connected by respective four-wire private lines between the respective computers and the respective central offices serving them; these connections are also through known means, and they establish these other computers as what are referred to in the telephone industry as remote drops or remote demarcation points.
With these connections of this example made, a communication between the master station demarcation point and the remote demarcation points (and thus between the master computer and the other computers) is established by bridging the remote demarcation points through their respective central offices to a central office within the same LATA. This latter central office communicates over a long line carrier with the central office to which the master station demarcation point is connected in the different LATA.
The goal of lowering the total charges for achieving the same ultimate communication can be accomplished by establishing an intermediate remote demarcation point and an intermediate master station demarcation point within the LATA of the ultimate remote demarcation points and by suitably interconnecting the intermediate remote demarcation point and the intermediate master station demarcation point. With this configuration or architecture, a single inter-LATA communication could then be made from the master station demarcation point where the master computer is located to the intermediate remote demarcation point. From there, communications would be established from the interconnected intermediate master station demarcation point to the ultimate remote demarcation points.
This general concept of obtaining lower leased line rates (referred to as decontamination) has, we believe, been recognized; however, this recognition has been within the context requiring the utilization of modems and digital conversion or processing techniques between the intermediate remote demarcation point and the intermediate master station demarcation point. This necessitates equipment which is relatively complex compared to our invention described hereinbelow. Therefore, we have found there is a need for a relatively simple apparatus and method by which analog communication signals can be sent through an architecture which is adapted to the existing telephone system, but which precludes incurring multiple inter-LATA rates and which couples the analog signals from the inter-LATA circuit to the intra-LATA circuit without requiring digital conversion or processing.